Compass Software Technology - Newsletter 04 - September 2012

Hi,
welcome to the latest Compass Software newsletter. The final part of our 'heating season' theme, this newsletter is going to look at another main source of heat, air-conditioning.

Air-conditioning systems are everywhere, you cannot walk into a shop or office today and not see either a ceiling or wall mounted unit. There have been many changes over the last few years especially such as the ban on using R22 gas, and many new systems have been installed. Looking back to when I worked in the facilities maintenance industry, the bulk of our callouts related to air-conditioning problems, so we will look at some of these issues in this newsletter.

Don't forget the benefits and abilities of our Regional Pro2 EAM software package will allow you to track and monitor your air-conditioning servicing and build up a lifespan picture of the ongoing health of your air-conditioning equipment.

In warmer countries most commercial air-conditioning installations are split systems. These are primarily used for cooling, whereas in Ireland, UK etc, they are generally dual purpose for both cooling and heating. A heat pump is simply an air conditioner that is reversible.

How they Work

The outdoor section consists of a fan, outdoor coil, compressor, and reversing valve.

Refrigerant (for more information see http://www.bis.gov.uk/files/file29101.pdf) circulates between the outdoor and indoor sections. It exists as either liquid, gas, or super high-pressure, high-temperature gas.

The compressor, compresses the gaseous refrigerant into the super high-pressure state. In summer cooling mode, the compressor this to the outdoor coil, where it condenses into liquid form, thus releasing its heat to the outdoor air.

The liquid refrigerant is sent back to the indoor coil where it is allowed to expand (boil into gas) as it passes through the coil, where air blown by the fan of the indoor section over the coil, absorbs heat from inside the building.

The refrigerant gas is then sent back to the compressor to be compressed into high-pressure gas and circulated through the outdoor coil, begining the cycle again.

In winter heating mode, the reversing valve shifts and the cycle is reversed. The compressor sends its high-pressure gas to the indoor coil where it condenses into liquid, releasing heat inside the building. The auxiliary heating element provides additional heat when the weather is very cold.

The liquid refrigerant is then sent to the outdoor coil, where it is allowed to expand (boil) back into gas and absorb heat from the outdoors.

The Indoor Section has a condensate pump and pipe to remove any water condensation on the outside of the coil. A filter helps keep the indoor coil clean.

A heat pump also has a defrost thermostat on the outdoor unit to control the defrost cycle of the unit when the system is operating in the heating mode. During the winter, the system reverses itself after a set time to release warmth to the outside and melt any frost or ice that may have formed on the external unit.

1. Filters
Air conditioners pass air through filters to clean it before cooling. This filters out pollutants and dust. The filter is a dense mesh type material that is attached to the inside of the plastic access cover, (see middle picture). A dirty filter will prevent adequate air flow across the coils. If a filter is really dirty, ice can build up on the coil in cooling mode. Symptoms of a dirty filter can be reduced cooling, reduced air flow, and water deipping condensate. It is recommended that you change / clean your filter at least every six months.

In the picture on the left you see the comparison of two filters from an air conditioner. The white filter has never been used, and the dark one is after use in a working air conditioner. The condition of the filter can be easily checked by your onsite technician (see middle picture).

If your filters are heavily soiled - Change more frequently, check for external environmental reasons for the dirt buildup. If a source is found (i.e. building works), check the impact on other systems. Once clogged, germs grows profusely in a dirty environment, creating another health hazard. Also if your filter is very dirty you should get the coil checked (dirty / blocked coils often smell).

2. Coils
For any system to run at its optimum performance, clean coils are extremely important. Clean coils positively affect energy efficiency, indoor air quality and long-term system performance.
An air-conditioning system has two finned coils, usually made of copper tubes with aluminum fins. The evaporator coil is the indoor coil and usually surrounds the fan like an oversized doughnut. The air is blown through it by the fan.

Maximum heat transfer is dependent on having clean coils. Even though the evaporator coil is protected with an air filter, over time they still get dirty. In addition, the evaporator coil and its condensate pump / pipe can become fouled with pollen, mold spores and other biocontaminants, all of which can have an adverse effect on indoor air quality.
With all the moisture around the evaporator coil, it can become a breeding ground for bacteria and mold. (See picture above right).
The condenser coil or outdoor coil is also exposed without the protection of a filter, the air moving over the coils contains dust, dirt, pollen, moisture and other contaminants so the coil gets dirty.

The cost of dirty coils An evaporator coil fouled with dirt and grime cannot supply proper heat transfer, which results in higher discharge pressures and greater energy consumption. Equipment operating with dirty coils can use up to 37 percent more energy than it does with clean coils. Accumulating dirt on coils inhibits heat transfer, which makes the compressor work harder, adding more heat and raising head pressures as much as 75 percent. Higher head pressures reduce the system's cooling capacity by as much as 30 percent, a condition that is most noticeable on the hottest days when cooling is required the most.
The higher temperatures and operating pressures caused by dirty coils can greatly shorten the life of the equipment.
The condenser coil is exposed to unfiltered outside air and elements such as dust, dirt, leaves, grass clippings and more. While the condenser coil does not affect indoor air quality, cleaning it at the same time as the evaporator coil will result in improved energy efficiency.
A coil cleaning program should be instituted when the coils are new and clean, and should be performed with enough frequency to prevent coil deterioration. This could be as often as four times a year.

3. Corrosion
With condensor units being outdoors and exposed to the elements, corrosion as the plant gets older can become a big issue.
Roof and side panels are often the main sites of deterioration and should be treated when first noticed. There is no reason for corrosion not be be spotted at a very early stage during maintenance cycles. Likewise lagging on the refrigerant pipes should be checked regularly. Corrosion could easily reduce the lifespan of a condensor unit by 5 years.

The picture on the right shows external corrosion at a late stage.This should have been rectified many years previously.

Occasionally, a system will develop a refrigerant leak. Symptoms of a refrigerant leak might include reduced cooling capacity, an outdoor unit that runs all the time, and high electric bills.

4. Location, Location
Many maintenance callouts are initiated because of complaints that the air-conditioning is blowing too hot or too cold. While coils and filters can often be the culprit, it can be the controller / sensor that is causing the issue. Temperature issues are sometimes caused by the location of the sensor or the layout of the room itself. If the sensor is exposed to drafts, near equipment that produces heat, in a dead air zone, too far away from the ac unit, etc., it will prove very difficult to get the temperature right for everyone in the room.

Check to see if anything is blocking access to your outdoor condensers, especially when they are wall mounted. The potential for a contractor to take a risk to complete a repair can be too real. You certainly do want to see the picture below.

5. Condensate Pumps & Leaks
Condensation pumps are connected to air conditioners to dispose of water condensate produced during the cooling process. This keeps the air conditioner from dripping in high heat. Maintaining a condensation pump properly keeps water from collecting and flooding the area where the air conditioner drains. Improper handling of air conditioning system condensate is one of the most commonly reported set of A/C system defects. Condensate problems can lead to leaks into the building, costly mold, ceiling, carpet or equipment damage, or even to complete A/C or heat pump system shutdown.

Clogging If your condensation drain tube connected to the pump is clogged it could be damaged or there could algae growing inside. Algae grows in wet conditions, so it is a common occurrence. If the condensate discharge pipe is fitted externally certain precautions need to be taken in winter to prevent the condensate from freezing, which could lead to the condensate backing up and leaking.

Leaking / Failed Pump If there are drips coming from your air-conditioning unit or the exit from your condensate pipe is dry then your pump may not be functioning. It may be something simple such as the check valve, a ball like object inside the unit, is stuck if it is blocked by debris or the pump may have failed. Pump failure is often caused by a clogged pump or filter. Failure may also be a result of a burned out motor, seized pump or an interruption in the electrical supply.

6. Visual Inspection
Many potential problems can be detected at an early stage by simply having a good look around your plant. The most obvious can be staining from rust, vibration or unusual sounds. Check filters when changed and your BMS for faults and when in doubt as we always say get it checked out. Also always ensure whoever is maintaining your plant is both competent and certified to carry out the work.